The Syrian Civil War is one of the most complicated and complex conflicts in Middle East, with countless of internal and external actors, blurring the borderlines between international and domestic politics. This study seeks out to analyse why two differently sized powers in the international hierarchy, namely Jordan and Turkey, supported rebel groups in the conflict and how this affected the Syrian armed opposition differently in South and North Syria respectively, creating two contrasting theatres of war. By viewing Jordan as a small power and Turkey as a middle power, this thesis argues that the size of two powers matters in their strategies towards a conflict and their ability to support rebels. The findings of this study, primarily based on a fieldwork conducted in Jordan and Turkey in the autumn of 2018 and spring of 2019, suggests that for a neighbouring small power like Jordan, having control in their external support to rebel groups is important when approaching conflict due to the risk of spillover effects from the Syrian Conflict. Whereas, for a middle power such as Turkey, supporting a wide number of different rebel groups simultaneously is possible, albeit challenging, as a tool to obtain limited influence and occasionally contest greater powers on the ground. These findings highlight important characters of the internationality of modern conflicts, such as the Syrian War.